The present invention relates to a plasma display which is a flat-type display unit used in receivers for broadcasting, terminals for computers or display for images. X3.
In the plasma display, short-wave ultraviolet rays (having a resonance line of 147 or 172 nm when xenon is used as inert gas) generated in a negative glow area in a small discharge space containing inert gas in a display panel is used as an excitation source to cause phosphor disposed in the discharge space to emit light to thereby make a display in color. A structure of a gas discharge cell of the plasma display as described in, for example, xe2x80x9cJapan Display ""92xe2x80x9d, pp 605-608 are depicted in FIGS. 5 and 6.
In the display panel of the plasma display, the resonance line for inert gas having a wavelength smaller than a resonance line of 253.7 nm of mercury vapor is used as an excitation source of the phosphor and a shortwave limitation thereof is a resonance line of 58.4 nm of helium. FIG. 5 schematically illustrates a reflective-type display panel of a general surface-discharge type color plasma display. A front substrate and a rear substrate are integrally combined with each other in fact. The front substrate is mainly composed of a pair of discharge sustaining electrodes formed in parallel to each other on a front glass substrate with a fixed distance therebetween and a dielectric layer formed on the electrodes to perform ac operation. The rear substrate is mainly composed of addressing electrodes formed on a rear glass substrate so that the addressing electrodes are disposed orthogonally to the discharge sustaining electrodes of the front substrate, barrier ribs each having the same structure (space, height and shape of side wall) made of glass having a low melting point and forming a partition between the adjacent addressing electrodes in order to prevent spread of discharge (to define the discharge area), and red (R), green (G) and blue (B) phosphor layers emitting red, green and blue light, respectively, and formed successively into a striped pattern so as to cover surfaces of grooves formed between the barrier ribs. The phosphor layers are formed by applying phosphor paste produced by mixing phosphor particles and vehicle with each other by using the screen printing method or the like after the addressing electrodes and the barrier ribs have been formed on the rear glass substrate and further a volatile component in the layers is removed by means of baking to complete the phosphor layers. The spaces between the barrier ribs, that is, barrier rib pitches defining the discharge spaces are the same for the red, green and blue phosphors as shown in FIG. 6.
The discharge space between the front and rear substrates is filled with discharge gas (mixed gas such as helium, neon and xenon) not shown to effect discharge between the discharge sustaining electrodes including X and Y sustaining electrodes so that the phosphor layers in a unit light emitting area (discharge spot) selected by the addressing electrodes are excited by vacuum ultraviolet rays produced by discharge of gas in the unit light emitting area to thereby attain visible emission. Amounts of light emitting in the unit light emitting area including the red, green and blue phosphor layers corresponding to the three primary colors are combined to make a display in color.
It is an object of the present invention to provide a plasma display having a structure easy to adjust a halftone color.
It is another object of the present invention to provide a plasma display capable of controlling a color temperature at the time of displaying the white color and displaying a high-quality image.
The luminance of a display panel and particularly a color panel of the plasma display is now being improved annually (lower than 450 cd/m2), although it is lower than that of a color television using a directview type cathode-ray tube (CRT) (peak luminance of 600 to 1000 cd/m2) and it desired to improve characteristics such as the luminous efficiency.
Further, the characteristics affecting the image quality include a color temperature at the time of displaying the white color. Particularly, the display for a computer terminal requires the same chromaticity and color temperature as those of paper. In the display using a cathode-ray tube, since the luminance for each of red, green and blue colors can be adjusted easily, the color temperature thereof (reproducible up to 9500 K or more) can be easily adjusted to provide the white color display satisfying the user""s request.
On the contrary, in the plasma display, since the luminance for each of red, green and blue colors cannot be adjusted independently, the color temperature for the white color display which is a representative of the halftone color cannot be adjusted to any value. Accordingly, it is strongly desired to develop the method of capable of adjusting the luminance for each of red, green and blue colors in the plasma display to any value.
In addition, the plasma display has a problem that discharge starting voltages by the red, green and blue phosphor films or layers are different and that is one cause to make it difficult to adjust the color temperature. Accordingly, it is strongly desired to develop the method of capable of reducing a difference in the discharge starting voltages by the red, green and blue phosphor layers in the plasma display.
Particularly, in the plasma display used in a computer terminal, the impossibility of adjusting the color temperature is a large problem.
The present invention realizes a plasma display having a structure easy to adjust the color temperature of the halftone color.
The above objects can be achieved by differentiating a space for at least one color, of spaces between barrier ribs for defining discharge spaces for red, green and blue colors of the display panel from the spaces for other colors.
The color temperature at the time of displaying the white color in a luminous display such as a plasma display is determined by the balance of the color temperatures of red, green and blue light emission constituting color components and the luminance thereof when phosphor materials for effecting red, green and blue light emission are the same. For example, when the color temperature of the white color is at a point of 6000 K on the locus of white color, the luminance of blue light emission can be made higher to thereby obtain the white color point having a higher color temperature. Further, the luminance can be made higher by reducing a discharge starting voltage, so that the substantially same effects can be attained. In addition, generally, the luminance can be made higher to thereby improve the display quality of halftone color.
Accordingly, in the plasma display of the present invention, the spaces between barrier ribs, which have the same size in the prior art, are varied in accordance with the light emission performance of red, green and blue phosphors to constitute the rear substrate.
Since adjustment of the color temperature of white color is made by adjusting the luminance balance of red, green and blue light emissions, the space between the barrier ribs corresponding to the position filled or applied with phosphor constituting a color component requiring a higher luminance is made wider than the spaces for other colors, so that an area of the phosphor layer producing the corresponding luminous color can be increased and the higher luminance can be obtained (FIG. 1). Further, the space between the barrier ribs at the position filled or applied with phosphor constituting a color component having too high a luminance for the luminance balance is made narrower than the spaces for other colors, so that an area of the phosphor layer producing the corresponding luminous color can be reduced and the luminance can be reduced (FIG. 2). Various combination of spaces between the barrier ribs constituting the red, green and blue phosphor layers can be made. There are various cases where only the space between the barrier ribs for the red phosphor layer is made larger or smaller, where only the space for the green phosphor layer is made larger or smaller, where only the space for the blue phosphor layer is made larger or smaller, where the respective spaces for the red, green and blue phosphor layers are different from one another (FIG. 3) or the like. In addition, the spaces for the barrier ribs can be set to various values allowed in the design of the display panel of the plasma display in accordance with the degree of widening or narrowing the spaces. For example, a difference between the spaces for two colors of the red, green and blue colors can be made 5%, 20% or 50% larger than a narrower space thereof. On the other hand, since the upper limit thereof is determined by the minimum space realizable in the display panel when the size of one pixel is constant, the upper limit can be set to an infinite value, while actually the minimum space is restricted depending on the degree of progress in the process technique, the strength of material, the discharge system and the like. It is no meaning that the upper limit is specified.
Further, since the discharge starting voltage can be reduced by widening the space between the barrier ribs, even the phosphor requiring a high voltage in order to obtain sufficient luminance can obtain the higher luminance by a lower voltage by widening the space.
According to the present invention, there can realize the plasma display capable of controlling the color temperature at the time of displaying the white color and displaying the high-quality picture.